Web winding control

ABSTRACT

An apparatus for controlling the winding or unwinding of rolls of web material, such as fabric and paper, at a constant web velocity on or from a roller connected with a controllable pumphydromotor combination. A main control of coarse continuous adjustment of the combination is used to produce a continuous primary speed curve which is a rough approximation of the desired theoretical speed curve of the hydromotor. A correction control for intermittent fine adjustment of the combination is superimposed upon said primary curve to produce a secondary continuous speed curve in steps which cross the corresponding parts of the theoretical curve at a considerable angle. A measuring device generates a signal in response to a predetermined deviation from the constant web velocity, said signal being used for periodically switching the correction control on and off.

United States Patent [72] Inventor Cornelis Johannes Van Os Zonstraat 100, Enschede, Netherlands [211 App]. No. 783,509 [22] Filed Dec. 13, 1968 [45] Patented June 15, 1971 [54] WEB WINDING CONTROL 8 Claims, 4 Drawing Figs.

[521 US. Cl 242/75.53 [51] Int. Cl B65h 59/38 [50] Field of Search 242/55, 67.1, 67.4, 67.5, 75, 75.43, 75.44, 75.45, 75.47, 75.5, 75.51, 57.53

[56] References Cited UNITED STATES PATENTS 2,351,264 6/1944 Harrington et al 242/7533 2,975,991 3/1961 Michel 242/7551 3,008,353 11/1961 Thompson.... 242/7553 X 3,043,535 7/1962 Chittenden... 242/7553 3,112,086 11/1963 Garten 242/7553 X 3,240,443 3/1966 Nitka 242/7553 t(seconds) Primary Examiner- Stanley N. Gilreath Assistant Examiner-Werner H. Schroeder Attorney- Stevens. Davis. Miller & Mosher ABSTRACT: An apparatus for controlling the winding or unwinding of rolls of web material, such as fabric and paper, at a constant web velocity on or from a roller connected with a controllable pump-hydromotor combination. A main control of coarse continuous adjustment of the combination is used to produce a continuous primary speed curve which is a rough approximation of the desired theoretical speedcurve of the hydromotor. A correction control for intermittent fine adjustment of the combination is superimposed upon said primary curve to produce a secondary continuous speed curve in steps which cross the corresponding parts of the theoretical curve at a considerable angle. A measuring device generates a signal in response to a predetermined deviation from the constant web velocity, said signal being used for periodically switching the correction control on and off.

L1 MAIN CONTROL L2 CORR ECTION CONTROL PATENTED Jurn 5197i SHEET 1 8F 2 T R A R m R P n(r. p.m.)

MMN CONTROL L2 CORRECTION CONTROL n(r.p.m.)

INVEN'IOR.

GDMVELM J1 VIM! 0.

PATENTED JUN] 5197i SHEET 2 BF 2 DIFFERENTIAL AMPLIFIER H ww TR 0 G ET NU P T U 0 W U EC R nm S w P T U 0 INVISN'IUR. CDRNELIJ d7- VRN 93 WEB WINDING CONTROL This invention relates to an apparatus for controlling the winding or unwinding of rolls of fabric, paper, and the like, at a constant web velocity, the winding roller being connected with a controllable pump-hydromotor combination.

Such an apparatus is known, for example, from my U.S. Pat. No. 3,480,191.

Driving a machine part (shaft, roller and the like) by means of a pump-motor combination of well known, the speed of such part being adjustable by controlling the pump output or the motor capacity. It is also known that, by suitable means, such as a dynamo, a pulser and the like, a signal can be generated which contains information on the web velocity or the speed of the shaft (in number or revolutions per minute), and that a deviation from the speed corresponding with such velocity can be corrected by means of this signal.

In the above apparatus according to my U.S. Pat. No. 3,480,191, two dosage pumps are used for measuring a deviation in the web velocity, the pressure differences of said pumps being a measure for the adjustment of the speed of the hydromotor which drives the winding or unwinding shaft. This leads to rather complicated apparatus, and it is accordingly an object of the present invention to simplify the control.

According to the present invention, there is provided an apparatus for controlling the winding or unwinding of rolls of fabric, paper, and the like at a constant web velocity, the winding roller being connected with a controllable pumphydromotor combination. A main control for coarse continuous adjustment of the combination is used to produce a continuous primary speed curve which is a rough approximation of the desired theoretical speed curve of the hydromotor. A correction control for intermittent fine adjustment of the combination is superimposed upon said primary curve to produce a secondary continuous speed curve in steps which cross the corresponding parts of the theoretical curve at a considerable angle. A measuring device generatesa signal in response to a predetermined deviation from the constant web velocity, said signal being used for periodically switching the correction control on and off.

The invention will now be described with reference to the accompanying drawings. In said drawings,

FIG. I shows a diagram incorporating the theoretical curve and the curve, as produced in the known apparatus;

FIG. 2 shows a diagram incorporating the theoretical curve and the curve as produced by means of the control according to the present invention;

FIG. 3 is a diagram of a complete installation according to the invention;

FIG. 4 is an electric block diagram of the manner in which a deviation in the speed is sensed.

The drive of a roll of material can be effected by means of a pump-hydromotor combination. It is immaterial whether the combination consists of:

a. a controllable pump and a noncontrollable motor b. a noncontrollable pump and a controllable motor c. a controllable pump and a controllable motor.

The essential feature is the control mechanism, which will hereinafter be considered for illustrative purposes to adjust the pump.

An example of the theoretical curve of a magnitude is shown in F IG. 1, together with the practical curve achieved by the adjustment. If there is a difference between a reference signal, associated with the theoretical curve, and the signal generated by the magnitude or in response to measurement, this difference is amplified (see FIG. 4) and applied to the positive output circuit if it is positive and to the negative output circuit if it is negative. A differential amplifier including a positive and a negative output circuit is conventional art, as described i.e. by G. B. Clayton in Wireless World," Oct. 1969, "Operational Amplifiers 9," and found in Differential/Cascode Amplifiers, R.C.A. -linear-integrated-circuits, File No. 327-Data-sheet, R.C.A. Electronic Components. In the given example, the pump can be adjusted for higher output by means of a relay connected to the negative output circuit and for lower output by means of a relay connected to the positive output circuit. Ideally, adjustment should be continued until an equilibrium has been reached, i.e. until the difference between the desired signal and the entrant signal is zero. Actually, however, this is impossible, because any form of control has the disadvantage that the desired curve configuration is inevitably only followed by approximation, i.e. the practical curve oscillates about the theoretical curve. It depends on the desired stability of the curve and/or on the accuracy of measurement whether a given amplitude will be sufficient or the deviations can still be measured.

If the speed of a shaft or the like must be kept constant in the manner described above, the amplitude of the deviations can indeed be kept so small as to remain within tolerable limits (cf. thermostat control).

The situation is different, however, in winding a web of material on a roll, or unwinding it from a roll, at a constant web velocity. This necessitates a continuously changing speed of the driving shaft (by reason of the increasing or decreasing diameter). That is to say, if a deviation An from the desired speed is measured and the speed is then corrected, the situation has meanwhile changed, and the corrective information given results in overcorrection or undercorrection. Such a control often leads to using rather high amplitudes because the theoretical curve must be intersected, while the correction frequency must be very high to produce a fair result. Apart from the fact that the actual curve produced in this way is often far from desirable, the large number of switchings per unit of time is not conducive to long life of the machine. An example of such a control is indicated by the dotted line in FIG. 1.

The present invention relates to an improvement of the above method of control. According to the invention, the output of the pump is continuously adjusted during the winding or unwinding process to produce an approximation, which may be very coarse one if necessary, of the theoretical speed curve of the winding shaft. A generally satisfactory adjustment is one as a function of the time. This can be done on the basis of the time required, for example, for fully winding or unwinding a roll. The main control will then ensure that during this time the pump is so adjusted that, at the desired web velocity, the speed of the hydromotor will be changed from a value associated with the smallest roll diameter to a value associated with the greatest roll diameter in the case of a winding process, and vice versa in the case of an unwinding process. Naturally, if this control should be used only, the curve actually produced would by no means correspond with the theoretical curve to a reasonable extent. By combining the above-described coarse or main control with a relay control, however, the following is achieved:

As soon as a deviation An from the desired speed is measured, a correction command is given to the pump. When the corrected speed curve has intersected the theoretical curve, the correction command is withdrawn, and the independent, continuous adjustment according to the main control is continued until the tolerable limit of An is again surpassed and sensed (see the diagram of FlG. 4). A comparison of FIG. I and 2 shows that, with one and the same speed tolerance An, not only is the number of corrections and hence the number of switchings reduced considerably, but a better adaption to the theoretical curve is obtained.

It has been shown experimentally that it is not absolutely necessary for the coarse control curve to be similar to the theoretical curve. lt has even been found to be generally more favourable to select a considerably shorter time for the coarse adjustment than the actual time required for the winding or unwinding process. One quarter of the winding time and even shorter periods have been found to produce good results.

FIG. 3 shows a diagram of a complete installation according to the invention. A stream of oil is passed by the pump P to the hydromotor M. The operative pressure of the oil acts on the piston rod side of the piston in the cylinder 1. As a result of this pressure, oil will be pressed from the cylinder compartment lb through the opened electromagnetically operated valve 2 and through the throttle valve 3 back into the tank 4. The throttle valve, which determines the coarse-control curve, is so adjusted that the time required to displace the piston in the control cylinder 1, and hence to adjust the pump, corresponds with the desired coarse adjusting period, i.e. with the curve Ll in FIG. 2.

This desired curve cannot, however, begin at zero speed, because the winding always requires a certain initial velocity, corresponding, for example, with the speed n,. It appears from the figure that this curve must be shiftedthrough a certain distance, which is effected by means of the correction control.

lf the speed is found to be too low, which can be measured, for example by comparing the voltage developed, by means of a tachometer-dynamo 5 directly driven by the web with the voltage developed by a control tachometer, as disclosed in U.S. Pat. No. 2,975,991, the correction valve 6 is opened electromagnetically to allow oil to pass from the cylinder compartment lb to the tank 4 through a throttle valve 7, so that the pump is adjusted by the L1+L2 control. As soon as the speed associated with the desired web velocity is a value An too high, the correction valve is closed and the pump is solely adjusted by the main control.

"'"T'ir'iiiifii'siir'EAEitunBErBe provided with a circuit arrangement by which the main valve 2 is closed when the speed is abnormally high. The control cylinder 1 will then be locked until the speed has again reached the desired value. The main valve is then reopened and continuous adjustment is resumed.

When the winding or unwinding process is finished, the piston in the control cylinder is in a position directly opposite to that required for a new winding cycle. By closing the main valve and opening the connecting valve 8, the piston is reset to its starting position, the total force exercised on the piston rod side b being greater than the total force exercised on the piston side a. unis be of aa'varage to rat ta; ili'dnirol mechanism 9, shown in dotted lines in FIG. 3, with a separate source of pressure medium, which may take the form of a small pump, a pressure cylinder, or even a source of compressed air.

Using a self-regulating pump as disclosed in Uidl at. No. 3,480,19l, a highly accurate control with a very small number of switchings can be obtained.

I claim:

1. An apparatus for controlling the winding or unwinding of rolls of web material, such as fabric and paper, at a constant web velocity on or from a roller connected with a controllable pump-hydromotor combination, said apparatus comprising a main control for coarse continuous adjustment of the combination to produce a continuous primary speed curve which is a rough approximation of the desired theoretical speed curve of the hydromotor, and a correction control for intermittent fine adjustment of the combination superimposed upon said primary curve to produce a secondary continuous speed curve in steps which cross the corresponding parts of the theoretical curve at a considerable angle, and a measuring device generating a signal in response to a predetermined deviation from the constant web velocity, said signal being used for periodically switching the correction control on and off.

2. An apparatus according to claim 1, wherein the pump is controllable and the main control and the correction control are operatively connected with the pump to control the output thereof.

3. An apparatus according to claim 2, wherein the main control is a piston-and-cylinder assembly connected with the pump for controlling the output thereof, one of the sides of said piston being under the operating pressure of said pump,

the other side of said piston communicatin with a main discharge line incorporating, successively, an e ectromagnetlcally operating main valve and a main throttle valve.

4. An apparatus according to claim 3, wherein the correction control is a correction discharge line communicating with the side of the piston opposite the side under the operating pressure of the pump, said correction discharge line incorporating, successively, an electromagnetically operated correction valve and a correction throttle valve.

5. An apparatus according to claim 3, wherein a connection valve is provided across the control cylinder adapted to establish a connection between said one side and the opposite side of said piston.

6. An apparatus according to claim 1, wherein the measuring device comprises a pickup for converting the winding velocity into an electric signal, a reference circuit'arrangement for a constant potential, and a differential amplifier including a positive and a negative output circuit, the signals of which can be picked up for actuating the correction control.

7. An apparatus according to claim 6, wherein said pickup is a tachometendynamo driven by the web.

8. An apparatus according to claim 1, which includes a circuit arrangement which eliminates the main control upon excessiyeppsitivedeyiation in thespeed. 

1. An apparatus for controlling the winding or unwinding of rolls of web material, such as fabric and paper, at a constant web velocity on or from a roller connected with a controllable pump-hydromotor combination, said apparatus comprising a main control for coarse continuous adjustment of the combination to produce a continuous primary speed curve which is a rough approximation of the desired theoretical speed curve of the hydromotor, and a correction control for intermittent fine adjustment of the combination superimposed upon said primary curve to produce a secondary continuous speed curve in steps which cross the corresponding parts of the theoretical curve at a considerable angle, and a measuring device generating a signal in response to a predetermined deviation from the constant web velocity, said signal being used for periodically switching the correction control on and off.
 2. An apparatus according to claim 1, wherein the pump is controllable and the main control and the correction control are operatively connected with the pump to control the output thereof.
 3. An apparatus according to claim 2, wherein the main control is a piston-and-cylinder assembly connected with the pump for controlling the output thereof, one of the sides of said piston being under the operating pressure of said pump, the other side of said piston communicating with a main discharge line incorporating, successively, an electromagnetically operating main valve and a main throttle valve.
 4. An apparatus according to claim 3, wherein the correction control is a correction discharge line communicating with the side of the piston opposite the side under the operating pressure of the pump, said correction discharge line incorporating, successively, an electromagnetically operated correction valve and a correction throttle valve.
 5. An apparatus according to claim 3, wherein a connection valve is provided across the control cylinder adapted to establish a connection between said one side and the opposite side of said piston.
 6. An apparatus according to claim 1, wherein the measuring device comprises a pickup for converting the winding velocity into an electric signal, a reference circuit arrangement for a constant potential, and a differential amplifier including a positive and a negative output circuit, the signals of which can be picked up for actuating the correction control.
 7. An apparatus according to claim 6, wherein said pickup is a tachometer-dynamo driven by the web.
 8. An apparatus according to claim 1, which includes a circuit arrangement which eliminates the main control upon excessive positive deviation in the speed. 